1. Field of the Invention
The present invention relates to a fuel injection controller of an internal combustion engine for calculating a fuel injection quantity in a combustion cycle based on a crank angle signal, which is detected in accordance with an angular position corresponding to rotation of a crankshaft of the engine, and for performing fuel injection control.
2. Description of Related Art
In an independent air intake internal combustion engine, a basic fuel injection quantity is set in accordance with an intake pressure, a throttle opening degree, an engine rotation speed or the like. A final fuel injection quantity is calculated by correcting the basic fuel injection quantity based on various parameters such as cooling water temperature, intake air temperature, atmospheric pressure or a gear position of a transmission. Fuel cutting control is also performed to change or cut the fuel injection quantity in accordance with various operation parameters such as engine rotation speed, vehicle speed, or a change in the throttle opening degree.
A technology related to the above scheme is described in JP-A-H04-81537, for example. In this technology, a fuel supply quantity is reduced from a steady-state value or cut for a predetermined time if deceleration is detected within a certain time after acceleration correction is performed.
If the processing ability of the CPU of an electronic control unit at the time when this technology was made is taken into consideration, then it would not have been possible for the above technology to consider the case where a series of operations, such as rapidly opening a throttle valve from a certain throttle opening degree and then rapidly closing the throttle valve, occurs in an extremely short time within one combustion cycle of the engine. Therefore, this technology cannot respond to an over-rich mixture condition, which can be caused by asynchronous fuel injection performed in accordance with the change in the throttle opening degree when the acceleration is required in the first stage by a driver and the throttle valve is rapidly opened. As a result, there is a possibility of reduction of engine rotation speed or engine stall.
However, in some cases, the over-rich mixture condition is not necessarily caused by the asynchronous fuel injection even in the case where the series of operations, namely, rapidly opening the throttle valve from a certain throttle opening degree and then rapidly closing the throttle valve, occurs in an extremely short time within a combustion cycle of the engine. There is also the possibility that an operating state of the engine is adversely affected if the fuel supply quantity is reduced or cut in a uniform manner.